It is known to provide a supercalender with a platform which is movable up and down at one side of a battery of rolls and can support one or more attendants as well as raise or lower the person or persons thereon to a desired level where such person or persons can reach a selected roll and/or a selected nip of two neighboring rolls. In many instances, the superimposed rolls of a calender cooperate with one or more guide rollers which define, for a running web of paper or the like, a meandering path extending through the nip of certain neighboring rolls as well as around one or more guide rollers. On most cases such a platform is provided on both sides of the supercalender. The platform is movable up and down at that side of the battery of rolls which confronts the guide roller or rollers. The platform is provided with a parapet which faces the one side of the battery of rolls and has a height such that an operator standing on the platform and leaning over the parapet can reach a selected roll, a selected guide roller and/or a selected nip of a pair of neighboring rolls in response to lifting or lowering of the platform to a particular level. Such platforms are practical because all an operator has to do is start a motor which drives the platform up or down until the platform reaches a level which is most convenient to afford access to a particular part of the calender, i.e., to a selected roll, to a selected nip and/or to a selected guide roller.
It is often necessary to carry out repair, maintenance and/or other work upon certain parts of a calender while the machine is in operation. This can result in serious injury to a careless person, e.g., to an operator who attempts to reach the nip of two selected rolls while the rolls are driven to advance a web of paper or the like along the predetermined path. Those levels of the platform at which an operator occupying the platform risks injury because the operator can lean over the parapet of the platform in order to reach a selected part of the machine are called danger levels because they are particularly dangerous to a careless, unskilled or tired operator while such person attempts to reach a dangerous zone (e.g., a nip) while the machine is in operation, i.e., in the process of advancing a web along a preselected path. The danger to an operator is particularly pronounced at a level where the operator can reach a web which is driven in a direction from the parapet of the platform toward the adjacent nip of two rolls.
It has been proposed to prevent access to one or more nips of rolls in a supercalender or an analogous web treating machine (hereinafter called calender for short) by providing a barrier or guard which prevents entry of fingers into that nip, at least into those nips which receives a web portion running away from an operator on the platform. A suitable guard is disclosed, for example, in commonly owned U.S. Pat. No. 4,867,055 granted Sep. 19, 1989 to Egon Hutter et al. for "Guard for the nips of rolls in calenders". As a general rule, the guard must extend in front of an entire nip, namely all the way from one end to the other end of each of the two rolls which define the nip. In many instances, the guard must be designed to define with each of the adjacent rolls a very narrow clearance having a width not in excess of 8 mm. This narrow clearance requirement creates problems when the nip is very long because the weight of the central portion of the guard causes the respective portion of the guard to flex downwardly with the result that the width of the upper clearance increases above 8 mm while the width of the central portion of the lower clearance is decreased accordingly, e.g., in some cases all the way to zero. Moreover, the width of the clearances between the guard and the adjacent rolls can vary in response to temperature changes. Consequently a guard is not an ideal solution for the problem of preventing injury to workmen attending to calenders having rolls of considerable length, i.e., to calenders where the width of the upper clearance between a platform and the adjacent roll is excessive and the width of the lower clearance between the guard and the adjacent roll is too small.